SP ability to handle multiple idp certs or idp metadata?

[Luke Alexander]

Hi,

I'd like to know if there is some documentation detailing how (if at all
possible?) an SP can be configured against an IDP who is in the process
of updating their certs - so that it may handle both old and new certs
(or old/new metadata) at the same time; meaning that when the time comes
for the old certificate to be expired there is a smoother transition to
the new?

Any help much appreciated!

Cheers,
Luke